A wide range of vehicles and methods are known for transporting human subjects. The design of these vehicles has generally resulted from a compromise that favors stability over maneuverability. It becomes difficult, for example, to provide a self-propelled user-guidable vehicle for transporting persons over ground having a surface that may be irregular, while still permitting convenient locomotion over ground having a surface that is relatively flat. Vehicles that achieve locomotion over irregular surfaces tend to be complex, heavy, and difficult for ordinary locomotion.